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Stabiliti daca numarul a = [tex](- \frac{1}{2} + \frac{1}{4} - \frac{1}{8} + \frac{1}{16} ) : (- \frac{1}{3} +\frac{1}{9} - \frac{1}{27} + \frac{1}{81} )[/tex] este pozitiv ,negativ sau nul. VA ROG REZOLVARE DE CLASA A 7-A DAU COROANA!!! VA ROG DIN TOT SUFLETUL E FORATE URGENTTTT

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Răspuns:

Explicație pas cu pas:

[tex]a=(-\dfrac{^{8)}1}{2}+\dfrac{^{4)}1}{4}-\dfrac{^{2)}1}{8}+\dfrac{1}{16}):(-\dfrac{^{27)}1}{3}+\dfrac{^{9)}1}{9}-\dfrac{^{3)}1}{27}+\dfrac{1}{81})=\\=(-\dfrac{8}{16}+\dfrac{4}{16}-\dfrac{2}{16}+\dfrac{1}{16}):(-\dfrac{27}{81}+\dfrac{9}{81}-\dfrac{3}{81}+ \dfrac{1}{81})=\\=\dfrac{-8+4-2+1}{16}:\dfrac{-27+9-3+1}{81}=\dfrac{-5}{16}:\dfrac{-20}{81}=\dfrac{-5}{16} *\dfrac{81}{-20}=\dfrac{81}{64}>0.[/tex]

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